#include<stdio.h>
int right1(char word[],int n)
{
	int sign=1;
	for(int i=0;i<n;i++)
	{
		if(word[i]<65||word[i]>90)
		{
			sign=0;
			break;
		}
	}
	return sign;
}
int right2(char word[],int n)
{
	int sign=1;
	for(int i=0;i<n;i++)
	{
		if(word[i]<97||word[i]>122)
		{
			sign=0;
			break;
		}
	}
	return sign;
}
int right3(char word[],int n)
{
	int sign=1;
	for(int i=0;i<n;i++)
	{
		if(i==0&&(word[i]<65||word[i]>90))
		{
			sign=0;
			break;
		}
		else if(i!=0&&(word[i]<97||word[i]>122))
		{
			sign=0;
			break;
		}
	}
	return sign;
}
int main()
{
	int n;
	scanf("%d",&n);
	char word[100];
	scanf("%s",word);
	int sign1=right1(word,n);
	int sign2=right2(word,n);
	int sign3=right3(word,n);
	if(sign1==1||sign2==1||sign3==1)
	{
		printf("true");
	}
	else
	{
		printf("false");
	}
	return 0;
}
